Hair styling irons having an electrically heated elongate tool are well-known, and commonly used for curling or straightening hair. One of the challenges facing the users of such appliances, particularly for professionals, is how to most efficiently achieve a desired styling effect. A number of factors influence the effectiveness of heat to shape the hair, these include intrinsic properties of an individual's hair, treatments agents applied to the hair (such as water or other softening agents), the time and temperature of the heat application, as well as the manner in which the hair iron is used (the size of a tress which is treated, the tension applied to the hair etc). Consistent results can be obtained most efficiently if these factors can be kept relatively constant for a specific treatment or if, for instance, they can be varied incrementally to provide a different level of treatment, however in the past this has been somewhat problematic. In particular, processing results can be variable if the operation is performed too fast, the processing time is too short and, therefore, the hair is not properly formatted, while processing hair for too long can damage the hair by overheating.
To address these issues it is known to provide hair curling irons with a timer to indicate an elapsed time from the start of the timer. US2006/0191888 describes a hair iron in which time and temperature are coordinated, and in which the user selects settings for the iron temperature and a desired curl tightness. The elapsed time is controlled such that for a selected curl tightness, the elapsed time is decreased with increasing temperature. However, there are drawbacks with this device associated with its ease of use. In operation, it requires the user to remember to start the timer by pressing a start button each time the iron is used, and for consistent results this button must be pressed at the same stage of the operation each time. Particularly when manipulating the iron behind the head it may be difficult to locate and press the start button. Moreover, programming the controller is a complex operation, in which three different buttons must also be operated to increase and decrease the settings for the timer. There is therefore a need for a hair styling iron having a timer which can be more readily used.
A further disadvantage of the curling iron of US2006/0191888 is that the coordination between time and temperature in this prior art manner takes no account of the mass of hair being curled, and the fact that the heat required increases with the mass of hear being curled. At any selected temperature a short tress is formatted more quickly than a longer tress, with the result that a short tress may be overheated, while a long tress is under-heated. There is a need for a hair styling iron having a timer which can mitigate this source of variability, to help users produce good results more predictably.
It is an object of the present invention to overcome or substantially ameliorate the above disadvantages or more generally to provide an improved electric hair styling iron.